I have the original Moor Depth Finder on my boat. Now and again it goes whacky giving me multiple zero's to depths of 139. Then a few blinks and its reading normal. I've checked it out with a new transdeucer and it still behaves the same. Question to the knowledgeable. Is this worth having the instrument repaired or is it better to get a new one? New, they are about $275-295, pending who has them in stock.